Let 'x+y=24' be equation 1 and '3x+5y=100' be equation 2
multiply equation 1 by 3 so 3x+3y=72 (this is equation 3) then subtract equation 2 from 3 3x+3y=72 - 3x-5y=-100 ---------------------- -2y=-28 divide by 2 on both sides -2y/2 = -28/2 -y = - 14 if -y= -14 then +y=+14 then put y in equation 1(or 2, you have a choice but 1 is easier) which will be x+y= 24 x+14=24 minus 14 on both sides x+14-14= 24-14 so x=10 <span>y=14 and x= 10 your answer </span>however on the exam paper you would write it like this :
'x +y =24' ⇒1 '3x+5y=100' ⇒2 x equation 1 by 3 3x+3y=72 subtract equation 2 from 3 3x+3y=72 - 3x-5y=-100 ---------------------- -2y=-28 -2y/2 = -28/2 -y = - 14 if -y= -14 then <span>+y=+14 </span>put y in equation 1 x+y= 24 x+14=24 x+14-14= 24-14 x=10
y=14 so 5 point answers and x=10 3 point answers
I know its long but you need to understand this. Hope it helped :)
